A study of the molecular and cellular nature of some of the interactions that occur during avian calcium metabolism is in process. Research efforts are directed primarily toward an elucidation of the role of carbonic anhydrase during the normal calcification process. The first phase of the work continues the characterization of a newly isolated avian carbonic anhydrase, which is unique among animal carbonic anhydrases in that it contains seven 1/2 cystines and requires the presence of dithiothreitol to maintain its activity in vitro. The second phase of the study probes the possible molecular effects of the environmental pollutants, DDT and DDE, on avian carbonic anhydrase. The latter study aims to begin a molecular clarification of the apparent negative influence of DDT and DDE on certain avian egg shelling processes. The rationale centers around the assumption that knowledge of the action of the pollutants on the avian systems now effected may assist in the prediction of the future possible deleterious effects of the pollutants on other species, including man.